The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The read head typically utilizes a spin valve sensor, also referred to as a giant magnetoresistive (GMR) sensor. The sensor at the ABS typically includes a barrier layer sandwiched between a pinned layer and a free layer, and an antiferromagnetic layer for pinning the magnetization of the pinned layer. The magnetization of the pinned layer is pinned perpendicular to the ABS and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields.
The volume of information processing in the information age is increasing rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD.
To achieve higher recording density, further miniaturization of recording bits is effective, which in turn typically requires the design of smaller and smaller components. The further miniaturization of the various components, however, presents its own set of challenges and obstacles.
The need for increasing the recording density of the HDD is pushing researchers to develop data recording systems that can read and record progressively smaller bit lengths in order to increase the density of data recorded on a magnetic medium. This has led to a push to decrease the gap thickness of a read head such as a GMR head. However, the amount by which such gap thickness can be decreased has been limited by physical limitations of sensors and also by the limitations of currently available manufacturing methods.
A self-pinned sensor in which the antiferromagnetic layer is reduced in thickness or removed completely so as to not provide a pinning field for the pinned layer structure provides a method to reduce the read gap thickness. However, the self-pinned sensor is sensitive to magnetic disturbances caused, for instance, by a head-media impact, which may flip the magnetic orientation of the free layer, thereby reversing the polarity of the amplitude of the output signal from the read head, often rendering the device useless.
Therefore, there is a need for an improved magnetic head and method of manufacture that enabling reduction of the read gap thickness while preserving the reliability of the magnetic head.